While first stating that I agree with much of what you've written above, I have to say that I come to some different conclusions.

We agree that at different times, some northern states have taken states rights positions on some issues. We agree that in some cases, southern states have opposed what might be called states rights positions. (The Fugitive Slave Law being an example as you stated). We agree that the southern states fought to maintain the institution of slavery since it was so important to their economies. But I would maintain that states rights was in fact the primary issue, when it came to the right of each state to separate itself from the federal government and control its own resources (human and otherwise) and destiny. The southerners fought to free themselves from the authority of the federal government, which they had helped to create.

Therefore, it is my view that the war WAS between the southern states and the federal government. When the southern states left, the federal government was in effect the government of the northern states. It was the federal government that made the determination to fight a war rather than accept secession. It was the federal government that directed and coordinated the people and the resources of the northern states to fight the war.

I have stated elsewhere on this forum my opinion that it was the personality of Abraham Lincoln who made the determination that secession would not be allowed to stand. It was the perseverance of Mr. Lincoln that held the northern war effort together and drove the war forward to an eventual military victory. I doubt that any other individual could have achieved that.

If the federal government had somehow collapsed when the southern states left, its doubtful to me that any individual northern state, or combination of northern states would have prosecuted a war to subjugate the southern states. It was the federal government that was the entity that the southern states wished to be free of, and it was the federal government that prevented them from achieving what they wished for.